The present invention is directed to receiver impedance calibration arrangements in full duplex communication systems.
Although this background and example embodiments of the present invention will be described using an example cabled or wired environment, practice of the invention is not limited thereto, i.e., the invention may be able to be practiced with other types of environments (e.g., on printed circuit (PC) boards, on-die).
To accomplish high-speed communication over a wire, it is important that both the transmitter and the receiver are impedance matched to the cable linking them. If such a match is not accomplished, some of the signal will be reflected back to the transmitter and again to the receiver at a later point in time where it will add error to the signal being sent. Manufacturing variation in both semiconductor circuit arrangements and a cable interconnecting the same, make calibration a necessary part of low-cost, high performance communications. Many techniques are available for providing the necessary calibration for a transmitter. They rely on sending a signal of some sort down the wire and looking at what is reflected back. This works wonderfully for transmitters, but is not easily implemented on a receiver. To implement such a function on a receiver, a transmitter may be added to the receiver inputs. This adds cost, complexity and capacitance to the receiver, all of which are non-desirable.
What is needed is a lower cost, simplistic, lower impedance arrangement to effect receiver impedance calibration.